Early Metabolic Adaptations to SGLT2 Inhibition in Heart Failure

The goal of this observational study is to learn about SGLT2 inhibition medications in patients with symptomatic heart failure who are clinically prescribed FDA-approved SGLT2 inhibitors. The main question it aims to answer is: * What are the impacts of SGLT2 inhibition on systemic metabolomic and proteomic profiles? Participants will be asked to do the following before and after being prescribed a SGLT2i. * Six-minute walk testd * Calf MRI with plantar flexion exercise * Blood sample collection

Inclusion Criteria: * Age ≥18 years * Clinically diagnosed HF documented in the patient's medical record * NYHA Class II-III functional status, according to the most recent clinical evaluation * Availability of an echocardiogram or cardiac MRI within the prior year * Stable HF medical therapy (no change in beta-blocker, ACE/ARB, ARNI or MRA for at least 4 weeks prior to screening) with the exception of diuretics * Planned initiation of on-label SGLT2i therapy Exclusion Criteria: * Receiving therapy with an SGLT2 inhibitor within 8 weeks prior to enrollment or previous intolerance to an SGLT2 inhibitor * Subject inability/unwillingness to perform a six-minute walk test * Acute coronary syndrome or unstable angina within the past month * Previous cardiac transplantation or implantation of a ventricular assist device * Any condition that will interfere with the completion of the study. This may include comorbid conditions or logistical factors that may impede successful completion of the protocol (e.g. inability to travel for follow-up visits) Absolute Exclusions for the Leg MRI Assessment (may still participate in blood sampling and six-minute walk testing): * ANY intracranial implants of any type other than dental fillings * ANY non-removable piercings, jewelry, or medicinal patch * ANY personal history of intraocular injury or fragment in or around the orbit that cannot be cleared through radiologic examination * ANY personal history of bullet, shrapnel, or stabbing wounds that cannot be cleared through radiologic evaluation. * ANY non-removable life assist device, pump, or prosthetic Possible Exclusions\*\* for the Leg MRI Assessment (may still participate in blood sampling and six-minute walk testing): * An intra-luminal implant, filter, stent, or valve replacement * A vascular clip or clamp * A surgically placed clip, clamp or band on visceral organs * A cardiac pacemaker or implanted cardiac defibrillator (ICD)##